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<head><meta charset="utf-8"><title>I-prioritize #73223 Test regression from stable to beta · t-compiler/wg-prioritization · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/index.html">t-compiler/wg-prioritization</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html">I-prioritize #73223 Test regression from stable to beta</a></h3>

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<a name="200482005"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200482005" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> triagebot <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200482005">(Jun 10 2020 at 21:53)</a>:</h4>
<p><span class="user-group-mention" data-user-group-id="2403">@WG-prioritization</span> issue <a href="https://github.com/rust-lang/rust/issues/73223">#73223</a> has been requested for prioritization.</p>



<a name="200489249"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200489249" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Santiago Pastorino <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200489249">(Jun 10 2020 at 23:04)</a>:</h4>
<p>we don't have a lot of information about this issue but is a stable to beta regression, not prioritized and not assigned for now</p>



<a name="200489263"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200489263" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Santiago Pastorino <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200489263">(Jun 10 2020 at 23:05)</a>:</h4>
<p>let's see if we have some information before the meeting</p>



<a name="200521915"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200521915" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200521915">(Jun 11 2020 at 09:25)</a>:</h4>
<p>Looking at the update by <code>djc</code> this looks like <code>P-critical</code> to me <span aria-label="oh no" class="emoji emoji-1f615" role="img" title="oh no">:oh_no:</span> We have a fairly easy way to trigger miscompilations here</p>



<a name="200522161"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200522161" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lcnr <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200522161">(Jun 11 2020 at 09:28)</a>:</h4>
<div class="codehilite"><pre><span></span><code><span class="k">fn</span> <span class="nf">main</span><span class="p">()</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w">    </span><span class="kd">let</span><span class="w"> </span><span class="n">split</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="k">match</span><span class="w"> </span><span class="nb">Some</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span><span class="w"> </span><span class="p">{</span><span class="w"></span>
<span class="w">        </span><span class="nb">Some</span><span class="p">(</span><span class="n">v</span><span class="p">)</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="n">v</span><span class="p">,</span><span class="w"></span>
<span class="w">        </span><span class="nb">None</span><span class="w"> </span><span class="o">=&gt;</span><span class="w"> </span><span class="k">return</span><span class="p">,</span><span class="w"></span>
<span class="w">    </span><span class="p">};</span><span class="w"></span>

<span class="w">    </span><span class="kd">let</span><span class="w"> </span><span class="n">_prev</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="nb">Some</span><span class="p">(</span><span class="n">split</span><span class="p">);</span><span class="w"></span>
<span class="w">    </span><span class="n">assert_eq</span><span class="o">!</span><span class="p">(</span><span class="n">split</span><span class="p">,</span><span class="w"> </span><span class="mi">1</span><span class="p">);</span><span class="w"></span>
<span class="w">    </span><span class="c1">//~^ fails with `left: 0, right: 1`</span>
<span class="p">}</span><span class="w"></span>
</code></pre></div>



<a name="200542074"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200542074" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Santiago Pastorino <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200542074">(Jun 11 2020 at 13:14)</a>:</h4>
<p>agreed <code>P-critical</code> IMO too</p>



<a name="200542106"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200542106" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Santiago Pastorino <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200542106">(Jun 11 2020 at 13:15)</a>:</h4>
<p><span class="user-mention" data-user-id="125250">@Wesley Wiser</span>, given that you've assigned it to yourself, thoughts?</p>



<a name="200542248"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200542248" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Wesley Wiser <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200542248">(Jun 11 2020 at 13:16)</a>:</h4>
<p>Seems fine to me. I'm making progress on a real fix but for <code>beta</code>, I think I'm just going to disable the optimization</p>



<a name="200542250"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200542250" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Santiago Pastorino <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200542250">(Jun 11 2020 at 13:16)</a>:</h4>
<p>have tagged as <code>P-critical</code> <span aria-label="+1" class="emoji emoji-1f44d" role="img" title="+1">:+1:</span></p>



<a name="200543342"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200543342" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Santiago Pastorino <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200543342">(Jun 11 2020 at 13:26)</a>:</h4>
<div class="codehilite"><pre><span></span><code>- &quot;Slice index becomes wrong (beta regression)&quot; [#73223](https://github.com/rust-lang/rust/issues/73223)
  - This is a regression from stable to beta
  - [It&#39;s also a fairly easy to trigger miscompilation](https://github.com/rust-lang/rust/issues/73223#issuecomment-642530618)
  - [Regressed PR was identified](https://github.com/rust-lang/rust/pull/69756)
  - Assigned to @**Wesley Wiser** who is already on it
</code></pre></div>



<a name="200543359"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200543359" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Santiago Pastorino <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200543359">(Jun 11 2020 at 13:26)</a>:</h4>
<p>does this sound like a good summary for the meeting?</p>



<a name="200544038"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize%20%2373223%20Test%20regression%20from%20stable%20to%20beta/near/200544038" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Wesley Wiser <a href="https://rust-lang.github.io/zulip_archive/stream/227806-t-compiler/wg-prioritization/topic/I-prioritize.20.2373223.20Test.20regression.20from.20stable.20to.20beta.html#200544038">(Jun 11 2020 at 13:32)</a>:</h4>
<p>Yeah</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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